1. Field of the Invention
The invention is with respect to fixing anchoring bars or the like in concrete structures such as concrete floors.
2. Description of the Prior Art
Presently, there are a number of ways in which parts may be anchored in concrete. If it is clear right from the start where anchoring bars or bolts are to be fixed in concrete before the concrete structure is made, the bars, which, at their ends, have a cross-bar or a hook, may simply be cast in place in the concrete. However, it is frequently not possible to see beforehand where such anchors are to be fixed. In such cases, holes for anchors are produced in the concrete floor or wall after curing and then plugs put in the holes so that the threaded rod may be put in each plug. Such plugs are, in the main, plugs of plastic material, kept in position by friction, metal expansion plugs with inner and outer cones, or compound plugs which are fixed in position by adhesive. Although, if plugs of plastic material are used, it is possible for the threaded rod to be unscrewed, such plastic plugs have their shortcomings inasfar as slipping is likely if there are changes in temperature, if there is a changing or shock-like load or if the concrete is cracked. Furthermore, on using plastic plugs, gripping forces are necessary in the connection to keep the plug in place. The properties of metal plugs or anchors, when there is a change in temperature or shock-loading or if the concrete becomes cracked (although there is a relatively high degree of slip in the last-named cases) are somewhat better, but in other respects, metal anchors or plugs have the same shortcomings as plastic plugs and furthermore may not be undone. This is furthermore true of adhesively fixed compound plugs, which, although generally not likely to become loose under loads and not responsible for gripping forces, have shortcomings with respect to changes in temperature and cracks in the concrete. Anchoring processes for use in hard concrete and which are completely free of trouble and which give safe connections, for the purpose of anchoring metal bars in croncrete, have not so far been worked out. Safe connections with concrete are, however, necessary. One idea coming to mind would be making the hole in the concrete wider in an inward direction but, however, there is no known way of drilling for readily producing such holes and if at all, it would seem that such holes might only be produced using complex drilling tools which would be able to be slipped in through the narrow mouth of a hole and then be increased in radius within the hole, at least in part, for making the parts of the hole inside the concrete larger in diameter. Such a process might be able to be used, although being very complex, if the holes might be kept clear of reinforcements within the concrete. There would be no certain way of not cutting the reinforcements and if reinforcements were in fact to be cut, the special-purpose drilling tools needed for producing holes becoming wider in an inward direction would be damaged.